Due to its characteristics of being easily applicable to various products and electrical properties such as a high energy density, a secondary battery is not only commonly applied to a portable device, but universally applied to an electric vehicle (EV) or a hybrid electric vehicle (HEV) and an energy storage system that is propelled by an electric motor. This secondary battery is gaining attention for its primary advantage of remarkably reducing the use of fossil fuels and not generating by-products from the use of energy, making it a new eco-friendly and energy efficient source of energy.
A battery pack for use in electric vehicles has a structure consisting of a plurality of cell assemblies connected in series, each cell assembly including a plurality of unit cells, to obtain high power. Also, the unit cell includes a positive electrode current collector and a negative electrode current collector, a separator, an active material, and an electrolyte solution, and allows repeated charging and discharging by electrochemical reactions between the constituent elements.
Recently, with the growing need for a high-capacity structure as well as utilization as an energy storage source, there is an increase in demand for a battery pack of a multi-module structure in which a plurality of battery modules including a plurality of secondary batteries connected in series and/or in parallel are assembled.
Because a battery pack of a multi-module structure is designed to have a plurality of secondary batteries arranged with a high density in a narrow space, it is important to easily discharge heat generated from the respective secondary batteries. One of the various methods of discharging heat generated from a secondary battery, a cooling method using a coolant is disclosed in Korean Patent Application Publication No. 10-2013-0062056.
FIG. 1 is a diagram illustrating the design of a cooling channel 10 according to a related art.
Referring to FIG. 1, the cooling channel 10 for cooling a secondary battery is illustrated. A refrigerant flowing in the cooling channel 10 enters an inlet 11 and exits an outlet 12. In the cooling channel 10 of the above structure, the secondary battery is more cooled at the inlet 11 side and is less cooled at the outlet 12 side. That is, the farther from the inlet 11 and closer to the outlet 12 the location is, the higher the temperature of the coolant is, so the cooling efficiency reduces.
The above problem of the related art causes a temperature gradient of the secondary battery, and the temperature gradient of the secondary battery leads to a performance gradient of the secondary battery. Finally, it connects with performance deterioration of a system such as a battery pack including the secondary battery. Therefore, there is a need for the design of a cooling channel to provide a uniform cooling effect.